Pyrolytic carbon nose for hypersonic vehicles

ABSTRACT

The present invention provides a spacecraft re-entry nose which makes use of the very marked anisotropy of pyrolytic graphite, which pyrolytic graphite is arranged in slices which are orientated so that the direction of least thermal conductivity is along the main axis of the nose whereas the direction of greatest thermal conductivity is at right angles to the surface of each slice. The slices are interconnected in pairs by three traversing pins of tungsten offset by a certain angle every two slices.

I I v Umted States Patent 11 1 -111 3,776,139

Lomand Dec. 4, 1973 [54] PYROLYTIC CARBON NOSE FOR 3,536,011 10/1970 Kinnaird 102/105 HYPERSONIC VEHICLES 3,428,473 2/ 1969 Langley 244/1 SS X I 3,152,548 10/1964 Schwartz 102/105 1 lnvemefl Gerard Leomand, Chavflle, 3,103,885 9/1963 Mclauchlan 244/117 A x France 3,095,162 6/1963 Keon 244/117 A [73] Assignee: Societe Nationale Industrielle Aerospafiale, Paris France Primary Exammer-Bemamm A. Borchelt Assistant ExaminerHarold Tudor [22] Flled: June 1972 Att0rneyl(arl W. Flocks [21] Appl. No.: 260,363

[57] ABSTRACT [30] Foreign Application Priority Data The present invention provides a spacecraft re-entry June 11, 1971 France 7121386 hose which makes use of the y marked anisotropy of pyrolytic graphite, which pyrolytic graphite is ar- 52 US. (:1 102/105, 244/1 ss ranged in Shees which are orientated so that the direc- 51 Int. Cl. F42b 13/00 Of least thermal conductivity is along the min 58 Field of Search 102/105, 49.4; axis of the nose Whereas the direction of greatest ther- 244 1 SS 117 mal conductivity is at right angles to the surface of each slice. The slices are interconnected in pairs by 5 References Cited three traversing pins of tungsten offset by a certain UNITED STATES PATENTS angle every Slices 3,596,604 8/1971 Corkery 102/105 6 Claims, 14 Drawing Figures Pmmnnm 41915 4 3776.139

SHEET 38F 3 Section a Section 0 considered cons/dered inthe /n the I direction of f direction of f Section b considered In the direct/on of g Sec tion b considered In the d/rect/on of g FIG.8

Section c considered in the I direct/on of h FIG. '90

Section c considered In the direct/on of h FIG!) I Section d Sect/on d considered considered 23 /n the in the direction of d/rec non of j sipated, andvarious. methodsare usedztosthat end.

1 2 PYROLYTIC CARBON NOSE FOR :HYPERSQNJC FIG. 3 is a partialv sectional view'portra ying the man- VEHICLES ner'in which pins are used to interconnect two'carbon slices when the latter are a i:jgi n i r3g; H

Hypersonic gliders designed toflyat high MaCIh-nurn- FIG. 4 shows in partial section the method of using bers. in excess of Mach 5 pose difficult coolingprobpins-for interconnecting two-carbon'slices whenthe lat-'- lems duringre-entry into the dense layers of he atmoter are spaced from eachother; 1 sphg e, and it well-known for example that-certain FIG. 5 iS a perspective Sl'IOWII'IgOfKhBv'StaCkCd.Cal'bOl'l. gliders must be capable of withstandin a .stm r h slices forming the nose of the hypersonic v'ehi'cl'e', in an' mal flux of ngafly v1:00 w z for approximately, g embodiment of this invention; and.

Seconds I 1*0 'FIG.;6 and FIGS. 7 through 10 and 7a through 10a Such a thermal environment the large amount are axial and cross-sectional views showing the arheat e-merjng thevstrucmre, particularly at thc:Stagna rangement of the pins for interconnecting the slices.

tionzpoim, which is the nose oft-he which ymusit,beidis Generally speak1ng, for laminar flowlconditiohs, the convection. flux along the conical portion. of the reentry'nose, asshown mare. -1,is'.given at anypoint M I th be t' dth I Among known me long use of whose abscissa is X byv Lees formula:

a socalled. heat sink, whichconsists in-usinga "massive block of some materialhavinga high meltingpo'int and highspecific heat, such aslhconel. Another solution based on a refractorymaterial-consists in using ei- 2o ther a nose made of a complex materiaL-coveredjwith ceramic or in providing some convenient armatuaecov:

"where qc isthe convection flux in kW/m q isthe convectionflux at the stagnation point,' is the distance along the cone from the apex' (in with Precmcklqd cle-amicr and? Qinfgmdf with metres- X RNcotan a s RN (1r/2 a) platmufn ais the half-angle of. the cone apex,

A thud Solution based onc-arbon rag-gmconsisyt s is the curvilinear abscissa (in metres), either in using a 0 P m P 9 Qarbgnl RN is the radius of the sphere (in metres), and A,B Protected from oxldallon by adePoslt'based-unimolybe arecoefficients whichdepend on the flow and the denum or in providing aconvenientsubstrate coveredi geometry I with a yrolytic carbon nose-cone, in-vwhich ca e he withthe geometricalcharacteristics established anddirection .of least thermal conductivity is atrightangles, the flow determined, it can be shown that the heat flux to the surface of the substrate. Such atechniquewas in} is. a decreasing function of the distance X along the fact described in U.S. Pat. No. 3,095,162. cone,- bey0ncla distance X- 2 X0, with:

HOW-vi: tliiSOlU-tlofis p t s i heretofore aoilot. It. can be shown further that the heat flux along a nose whereas the direction of greatest thermal Conducgive complete satisfaction in that theheatflux is not cone underturbulent conditions is related to the flux properly distributed through the material forming-the 40' under laminar conditions and that this flux is likewise nose of the vehicle. a function of X.

The present invention provides aspacecraftre-entry Since the heat flux andhence the temperature de-' nose which makes use of the very marked anisotrdpy-. ,of. pend on the, distance X from the virtual apex of the pyrolytic graphite, which pyrolytic graphiteis arranged cone, in accordance with this invention the nose of thein slices which are orientated that. the.,.directipn of vehicle is made up of pyrolytic carbon slices, as shown least m l conductivity is alonglhrnain axis f in FIG. 2, that are so orientated that the axis 0" parallel to the axis oxrepresents the direction of least ther tivity is at right angles to Surface ogeach [slimy mal conductivity, whereas the axes ?a and b at right A specific assembly method utilizing interconnecting, 50. pins made of a material with va hig melting-point fur: thennore enables the slices to be secured to'one another. i v

Thedescription which follows with reference-to the accompanying non-limitative exemplary-drawings of an embodiment of the invention, as applied to thenoseof a hypersonic vehicle designed for speeds of over Mach 5 and comprising pyrolytic graphite slices in orientated directions, will give a clear understandingof how .theinvention can be carried into practice,

thermal conductivity.

Thus the heat flux exhibits a profile of the kind shown in- FIG. 1, in which it will be seen that the temperature is due essentially to the entering convection flux and that conduction in the x direction is negligible.

FIG. 5 showsan embodiment of this invention in the case of a hypersonic vehicle nose weighing approximately 1,500 kg and capable of withstanding the loadcase of a heat flux of 100 kW/m.

A nose of this kind, generally designated by reference In the drawings: numeral 1 in the drawings, consists of a stack of pyro lytic carbon-slices-designated 3 throughl22, andthis stack includes a spherical termination 2,} while an arrangementxof interconnecting pins, to hich further reference. will be had hereinafter, is use to unite the several noseelements.

FIG. 1 is a schematic axial showing of the profile of.- the heat fluxes through a nose for hypersonic vehicles in accordance with this invention, dnring the phaseof re-entry into the, atmosphere;

angles to the faces represent the direction of greatest ings engendered by 500 seconds of level flight in the- FIG. 2 shows schematica ly in-per pe ti h r n- Obviously, the pyrolytic carbon slices are orientated tation of the pyrolytic carbon slices and the 8 291 P in. the. manner described precedingly, and the overall sitions of the connecting pins according to. this invenconfiguration is such as to satisfy the aerodynamic retion; 7 quirements in operation. I

Interconnection, which consists in joining two consecutive slices and which is illustrated in partial section in FIGS. 3 and 4, is accomplished by means of three pins made of a material having a high melting point, such as tungsten, inclined at an angle to the nose axis. This inclination prevents the two slices from separating by an amount in excess of dx defined by:

where d is the clearance of the pins in their holes at the temperature considered.

Further, each pair of slices is united by three pins, as shown in FIGS. 6, 7 through 10, and 7a through 10a.

In order to prevent the pins from overlapping, their positions must be rotated through a certain angle every two slices.

In the embodiment of this invention, the pins 23 a, b, c, to 23 a, b, c in FIG. 5 are mutually offset by an angle equal to 27r/9, which results in an arrangement similar to that shown in FIGS. 6, 7 through 10, and 7a through 10a.

The pairs of slices can readily be assembled together by means of the pins, provided that the latter are inserted starting from the spherical portion of the nose and that an adequate interconnecting element is positioned between the last slice and the structure of the vehicle.

Further, possible alternative embodiments leading to improved slice interfaces could consist in:

- glueing the slices together,

- joining the slices with a cement in between,

- or inserting an intermediate felt of thin graphite.

It goes without saying that the specific form of embodiment hereinbefore described has been given by way of example only in order toclearly show the possibilities inherent in the invention, and that changes and substitutions may be made. without departing fromthe scope of the invention.

Iclaim:

1. A pyrolytic carbon nose for hypersonic vehicles,

having a termination point and a generating axis, comprising pyrolytic carbon, stacked, oriented slicescharacterized'in that traversing pins, inclined toward'said terminal point with respect to said nose generating axis, interconnect said slices in pairs producing a global linking of all the slices together.

2. A hypersonic vehicle nose as claimed in claim 1, further characterized by the fact that said pins are made of tungsten and are cylindrical in shape.

3. A hypersonic vehicle nose as claimed in claim 1,

further characterized by the fact that bores are formed I slices. 

1. A pyrolytic carbon nose for hypersonic vehicles, having a termination point and a generating axis, comprising pyrolytic carbon, stacked, oriented slices characterized in that traversing pins, inclined toward said terminal point with respect to said nose generating axis, interconnect said slices in pairs producing a global linking of all the slices together.
 2. A hypersonic vehicle nose as claimed in claim 1, further characterized by the fact that said pins are made of tungsten and are cylindrical in shape.
 3. A hypersonic vehicle nose as claimed in claim 1, further characterized by the fact that bores are formed in said slices for receiving said pins with clearance therein.
 4. A hypersonic vehicle nose as claimed in claim 1, further characterized by the fact that each pair of said slices is united by three of said pins.
 5. A hypersonic vehicle nose as claimed in claim 1, further characterized by the fact that the positioning of said pins is offset by a certain angle every two slices.
 6. A hypersonic vehicle nose as claimed in claim 1, in which a felt of thin graphite is inserted between said slices. 